package com.xk._01基础篇._02动态数组;

/**
 * @description:
 * @author: xu
 * @date: 2022/9/14 19:14
 */
@SuppressWarnings("unchecked")
public class ArrayList<E> {
    /**
     * 元素的容量
     */
    private int size;

    /**
     * 所有的元素
     */
    private E[] elements;

    private static final int DEFAULT_CAPACITY = 10;
    private static final int ELEMENT_NOT_FOUND = -1;

    public ArrayList(int capacity){
        capacity = Math.max(capacity, DEFAULT_CAPACITY);
        elements = (E[]) new Object[capacity];
    }

    public ArrayList(){
        this(DEFAULT_CAPACITY);
    }

    /**
     * 清除所有元素
     */
    public void clear() {
        for (int i = 0; i < size; i++) {
            elements[i] = null;
        }
        size = 0;
    }

    /**
     * 元素的数量
     * @return
     */
    public int size() {
        return size;
    }

    /**
     * 是否为空
     * @return
     */
    public boolean isEmpty() {
        return size == 0;
    }

    /**
     * 是否包含某个元素
     * @param element
     * @return
     */
    public boolean contains(E element) {
        return indexOf(element) != ELEMENT_NOT_FOUND;
    }

    /**
     * 获取index位置的元素
     * @param index
     * @return
     */
    public E get(int index) {
        rangeCheck(index);
        return elements[index];
    }

    /**
     * 设置index位置的元素
     * @param index
     * @param element
     * @return 原来的元素ֵ
     */
    public E set(int index, E element) {
        rangeCheck(index);
        E old = elements[index];
        elements[index] = element;
        return old;
    }

    /**
     * 添加元素到尾部
     * @param element
     */
    public void add(E element) {
        add(size, element);
    }

    /**
     * 在index位置插入一个元素
     * @param index
     * @param element
     */
    public void add(int index, E element) {
        rangeCheckForAdd(index);
        ensureCapacity(size + 1);

        for (int i = size; i > index; i--) {
            elements[i] = elements[i-1];
        }
        elements[index] = element;
        size++;
    }

    /**
     * 删除index位置的元素
     * @param index
     * @return
     */
    public E remove(int index) {
        rangeCheck(index);
        E old = elements[index];
        for (int i = index + 1; i < size; i++) {
            elements[i-1] = elements[i];
        }
        elements[--size] = null;
        return old;
    }

    public void remove(E element){
        remove(indexOf(element));
    }

    /**
     * 查看元素的索引
     * @param element
     * @return
     */
    public int indexOf(E element) {
        if (element == null){
            for (int i = 0; i < size; i++) {
                if (elements[i] == null){
                    return i;
                }
            }
        } else {
            for (int i = 0; i < size; i++) {
                if (element.equals(elements[i])){
                    return i;
                }
            }
        }
        return ELEMENT_NOT_FOUND;
    }

    /**
     * 保证要有capacity的容量
     * @param capacity
     */
    private void ensureCapacity(int capacity) {
        int oldCapacity = elements.length;
        if (oldCapacity >= capacity) return;
        //新容量为旧容量的1.5倍
        int newCapacity = oldCapacity + (oldCapacity >> 1);
        E[] newElements = (E[]) new Object[newCapacity];
        for (int i = 0; i < size; i++) {
            newElements[i] = elements[i];
        }
        elements = newElements;
    }

    private void outOfBounds(int index) {
        throw new IndexOutOfBoundsException("Index: " + index + ", Size: " + size);
    }

    private void rangeCheck(int index) {
        if (index < 0 || index >= size){
            outOfBounds(index);
        }
    }

    private void rangeCheckForAdd(int index) {
        if (index < 0 || index > size){
            outOfBounds(index);
        }
    }

    @Override
    public String toString() {
        StringBuilder string = new StringBuilder();
        string.append("size=").append(size).append(", [");
        for (int i = 0; i < size; i++) {
            if (i != 0){
                string.append(", ");
            }
            string.append(elements[i]);
        }
        string.append("]");
        return string.toString();
    }
}